The disclosure relates to wavelength-division multiplexing and demultiplexing, and more particularly to compact two-port devices.
Wavelength-division multiplexing (WDM) is a technology that multiplexes (e.g., adds) a number of distinct wavelengths of light onto a single optical fiber and demultiplexes (e.g., divides) a number of distinct wavelengths of light from a single optical fiber, thereby increasing information capacity and enabling bi-directional flow of signals. Multiple optical signals are multiplexed with different wavelengths of light combined by a multiplexer at a transmitter, directed to a single fiber for transmission of the signal, and split by a demultiplexer to designated channels at a receiver. By combining multiple wavelengths of light into a single channel, WDM assemblies and associated devices can be used as components in an optical network, such as a passive optical network (PON).
In certain applications, a three-port device may be used as an optical add-and-drop multiplexer (OADM). However, in other applications, the three-port device is too large and/or too complicated to manufacture. Further, in some applications, long fibers at port ends of the three-port device require extra care to avoid damage. For some applications, a two-port device may be used instead.
FIG. 1 is a cross-sectional top view of a two-port device 100. The two-port device 100 includes a first subassembly 102(1) and a second subassembly 102(2) in optical communication with the first subassembly 102(1). The first subassembly 102(1) includes a first port 104(1), a first ferrule 105(1) (e.g., ceramic), a first fiber optic collimator 106(1) having a first capillary 108(1) (e.g., glass) and a first fiber 110(1), and the first subassembly 102(1) further including a first collimating element 112(1) (e.g., C-lens or collimating lens, G-lens or gradient-index (GRIN) lens). The first fiber 110(1) is positioned within the first capillary 108(1). Similarly, the second subassembly 102(2) includes a second port 104(2), a second ferrule 105(2) (e.g., ceramic), a second fiber optic collimator 106(2) having a second capillary 108(2) (e.g., glass) and a second fiber 110(2), and the second subassembly 102(2) further including a second collimating element 112(2) (e.g., C-lens or collimating lens, G-lens or gradient-index (GRIN) lens). The second fiber 110(2) is positioned within the second capillary 108(2). A filter 114 having a thickness T1 is positioned between the first collimator 106(1) (and the first collimating element 112(1)) and the second collimator 106(2) (and the second collimating element 112(2)). The first collimating element 112(1) and the second collimating element 112(2) are required in order to transmit a multiplexed signal from the first subassembly 102(1) to the second subassembly 102(2) due to the thickness T1 of the filter 114, a first air gap G1(1) between the first collimating element 112(1) and the filter 114, and a second air gap G1(2) between the filter 114 and the second collimating element 112(2). In other words, as a multiplexed signal is transmitted between the first port 104(1) and the second port 104(2), the multiplexed signal must travel through the first collimating element 112(1) and the second collimating element 112(2).
FIG. 2 is a cross-sectional top view of a two-port device 200. The two-port device 200 includes a first subassembly 202(1) and a second subassembly 202(2) in optical communication with the first subassembly 202(2). The first subassembly 202 includes a first port 204(1), a first fiber optic collimator 206(1) having a first ferrule 208(1) and a first fiber 210(1) with a first collimating element 212(1) (e.g., graded-index fiber segment), and a filter 214. The first fiber 210(1) is positioned within the first ferrule 208(1). Similarly, the second subassembly 202(2) includes a second port 204(2), a second fiber optic collimator 206(2) having a second ferrule 208(2) and a second fiber 210(2) with a second collimating element 212(2) (e.g., graded-index fiber segment). The second fiber 210(2) is positioned within the second ferrule 208(2). A filter 214 having a thickness T2 is positioned between the first ferrule 208(1) (and first collimating element 212(1)) and the second ferrule 208(2) (and the second collimating element 212(2)). The first collimating element 212(1) and the second collimating element 212(2) are required in order to transmit a multiplexed signal from the first subassembly 202(1) to the second subassembly 202(2) due to the thickness T2 of the filter 214 and an air gap G2 between the filter 214 and the second ferrule 208(2). In other words, as a multiplexed signal is transmitted between the first port 204(1) and the second port 204(2), the multiplexed signal must travel through the first collimating element 212(1) and the second collimating element 212(2).
Referring to FIGS. 1 and 2, as noted above, these two-port WDM devices 100, 200 require collimating elements in the light path to function properly (among other reasons (e.g., for economic reasons, engineering reasons, mass-production reasons, etc.)) which adds to the size, manufacturing complexity, and/or cost, etc.
Accordingly, there is a need for two-port devices that are reliable, cost effective, and/or user friendly, and/or have a compact form-factor, easy replication, and/or versatility.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.